Primary galvanic cell



Patented Dec. 19, 1950 UNITED STATES PATENT `OFFICE PRIMARY GALVAN IC CELL Nelson C. Cahoon, Lakewood, Ohio, assignor, by

mesne assignments, to Union Carbide and Carbon Corporation, a corporation of New York Application December 14, 1944, Serial N o. 568,137

Claims. (Cl. 13G-142) This invention relates to primary galvanic cells and refers more particularly to such cells ofthe dry type.

In the conventional dry cell having a zinc electrode, a carbon electrode, a depolarizer mix of manganese dioxide and carbon, and an aqueous ammonium chloride electrolyte, a cereal paste. usually of corn starch or the like.' is used to immobilize the electrolyte and to separate the zinc anode from the depolarizer mix. To maintain adequate separation the paste layer must be quite thick. and consequently it undesirably lessens the quantity of depolarizer mix that can be present in the cell. Sometimes a molded bobbin of depolarizer mix is wrapped with a layer of cotton fabric or certain synthetic organic materials, and it has been suggested that a bobbin of depolarizer mix be coated with a layer of organic resin. Both of these expedients are intended to diminish the thickness of the paste layexin the dry cell, but neither eliminates the need for a cereal'paste. Another expedient that has been used with some success is to employ a paper liner which has been coated with paste to separate the zinc anode from the depolarizer mix, but, again, the use of paper does not eliminate the need for paste, and moreover paper increases the internal resistance of the cell to a serious degree.-

The use of a cereal paste in the construction of dry cells has several disadvantages among the more important of which are difllculties involved in the preparation of a paste of uniform composition and viscosity, the tendency of the cereal to hydrolyze in the presence of Y zinc chloride, and the reaction which occurs between the products of such hydrolysis and the manganese dioxide in the depolarizer mix.

In attempts to avoid the use of cereal paste, it has been proposed that a water soluble alkyl cellulose ether be substituted for cereal paste as a thickening agent for the electrolyte in the inter-electrode space. Dry cells using such materials give fairly satisfactory initial performance, but after a few months storage give very poor service because the viscous cellulose ether dition that it can be handled without damage by automatic machinery in cell manufacture. It should retain enough strength after assembly of a cell to prevent its accidental rupture or perforation and the consequent short-circuiting of the cell. Since the diaphragm in a dry cell occupies space to the exclusion of active material, the diaphragm should be as thin as possible so that the space it occupies is reduced to a minimum.

Chemically, a dry cell diaphragm must be inert. It must not react with the other elements of the cell and must undergo no chemical change which would interfere with proper cell operation. Otherwise,v a cell would have but a short shelf or service life. The diaphragm material must be resistant to chemical attack by the electrolyte, the zinc electrode, and the depolarizer mix with which it is in Contact and, further, must resist attack by the products of the chemical reactions which take place within the cell. Yet it must not hamper ready diffusion of such reaction products.

Furthermore, if the diaphragm is situated next to the zinc it must make uniformly good wet contact therewith over the entire active surface of the electrode, because imperfect contact leads to high internal resistance and premature corrosion and pitting of the zinc. l

Still further, the diaphragm should absorb and retain a large volume of electrolyte relative to its own total volume, that is, should be bibulous solution is to a considerable extent absorbed even when compressed between the zinc electrode and the depolarizer mix, and under these conditions it should not unduly increase the internal electrical resistance of the cell in which it is used.

These numerous requirements have heretofore prevented the commercial use of unpasted diaphragms in dry cells, for no diaphragm which satisfactorily meets all of these requirements has heretofore been available. Despite the many disadvantages of cereal paste, the vast majority of dry cells are made using paste.

It is the principal object of the present invention to provide a dry cell diaphragm which satisfactorily meets all the requirements for such diaphragms and which makes possible the elimination of cereal paste in dry cell construction. Another important object is a dry cell having improved service characteristics.

The invention by means of which these objects are attained is based upon the discovery that a nonbrous, nonporous lm composed of certain organic film-forming compounds is a highly satisfactory diaphragm material for dry cells, provided such fllm is suitably protected from solution and subsequent `dispersion in dry cell electrolyte, One group of film-forming materials which when so protected are suitable for be used.

`ganic nonbrous nlm-forming material.

of these diaphragms is their nlm base.

the purposes of the invention comprise the normally water-soluble alkyl cellulose ethers, and although the invention is not limited to any particular nlm-forming material, it will be described with particular reference to this group and specifically to methy1 cellulose which has been found to be particularly desirable.

In accordance with the invention a lm composed of alkyl cellulose ether normally soluble in dry cell electrolyte may be protected from excessive solution and dispersionr in such electrolyte in a variety of ways. For instance, a lllm which would otherwise be too readily soluble in electrolyte may be backed by a suitable electrolyte-.insoluble material to form a composite diaphragm or, alternatively, such a nlm may be treated with an insolubilizing agent; or both expedients may y In the accompanying drawing:

tions of a composite dry cel'l diaphragm embodyj ing the invention; A

Fig. 2 is simi/lar to Fig. 1 but illustrates a modifled form of vdiaphragm embodying the invention;

Fig. 3 is similar to Figs. 1 and 2 but illustrates another modification of the diaphragm of the invention;

Fig. 4 is an' elevational view partially in section of an otherwise conventional round dry cell provided with a diaphragm of the type shown in Fig. 1; and Y Fig. 5 is a side elevational view partially in section of a battery of fiat dry cells provided with diaphragms of the type shown in Fig. 3.

The essence of the invention lies in the provision of a dry cell diaphragm composed of an orthough there are several types of diaphragms embodying the invention, a common feature -of all Methyl cellulose is a suitable material for this film base. It is available on the market in a number of grades identified by the viscosity of a 2% aqueous solution of the material at C. Grades having viscosities ranging from 15 to 4000 centipoisesunder these conditions are satisfactory for th purposes of this invention.

Suitable films may be'prepared from aqueous solutions of methyl cellulose containing about 1%' to 15% methyl cellulose by Weight depending on the viscosity. For example, dry methyl cellulose in the desired quantity is mixed with Water which is at a temperature of 80 C. to 100 C. and the mixture is allowed to stand until the methyl cellulose is thoroughly wet. The mixture is then cooled, suitably in an ice bath, until solution is complete. poured on a smooth surface, such as a horizon-l tally arranged glass plate, and the water is evaporated from the solution. After evaporation of the water, a thin, .tough nlm is produced which vmay readily be stripped from the smooth surface.

A lm of methyl cellulose so producedis undesirably soluble in dry cell electrolyte. In one embodiment of this invention it is protected from excessive solution and dispersion in electrolyte by backing it with a separate electrolyte-insoluble material, thus forming a composite diaphragm to form a diaphragm of the type illustrated for example in Figs. 2 and 3.

One form of composite diaphragm embodying A thin layer of'this solution is then the invention consists of a film of electrolytesoluble alkyl cellulose ether backed by a film of regenerated cellulose. In a dry cell this composite diaphragm is placed with the regenerated cellulose backing adjacent to the depolarizer mix and the alkyl cellulose ether lm adjacent to the zinc electrode. Cells containing such a diaphragm combination possess particularly good keeping qualities but their successful use is limited to those applications in which discharge conditions do not require rapid diffusion of reaction products to maintain satisfactory operating voltages.

Another, and preferred, composite diaphragm consists ol an electrolyte-soluble film of alkyl celluloseether backed by an alkyl cellulose ether lm which has been subjected to an insolubilizing treatment. This type of diaphragm is placed in a dry cell with the electrolyte-soluble nlm adjacent to the zinc electrode and the insolubilized lm adjacent to the depolarizer mix.

A suitably insolubilized lm for use in the composite diaphragm may be prepared from an aqueous solution oi methyl cellulose to which an insolubilizing agent has been added. Suitable insolubilizing agents are organic polybasic acids, including aliphatic carboxylic, aromatic carboxylic and phenol carboxylic acids. Citric, phthallc, tricarballylic, tartaric, and malic acids, as well as gallic, digallic and similar acids commonly known as tannic acids are typical of the acids that 'may be used. Insolubilized films may be prepared by casting and drying a methyl cellulose containing tannic acid. but if any other acid from this group is used, heat treatment of the nlm produced on casting and drying the solution is required for insolubilization. A suitable film-forming solution may contain about 1% to 15% methyl cellulose by weight and about 0.1 part to 1.5 parts of tannic acid for each part by weight of methyl cellulose. This solution when cast and dried in the usual way produces a film with many of the physical characteristics of the plain methyl cellulose nlm but one which is at least partially insoluble in dry cell electrolyte.A

A somewhatv more desirable insolubilized iilm for use in the composite diaphragm is prepared from a methyl cellulose solution containing citric acid as an insolubilizing agent. The quantity of citric acid present in the solution may be about 0.01 to 1 equivalent weight of citric acid for each Ce unit of methyl cellulose, one equivalent of,

citric acid being one-third of its formula weight and a Cs unit being the basic unit of the complex methyl cellulose molecule. Good lms have been formed for example from aqueous solutions tion are at least partially insoluble in dry cell electrolyte and have desirable properties after heat treatment at a temperature of about C. to 250 C. The time of heat treatment in preparing a lm of this type depends not only on the temperature of the heat treatment but on the quantity of citric acid in the illm, the higher the temperature and the greater the quantity of citric acid employed, the shorter the time of treatment to attain a given degree of insolubility. Ordinarily, the film is heated for a time between a few seconds and ninety minutes. Excellent films have been obtained by heating 8 to 10 minutes at 205 C. j

`A backing film produced from a solution containing tannic acid or citric acid as described, although substantially insoluble in dry cell electrolyteVabsorbs limited but substantial quantities of electrolyte to produce an elastic, electrolyte-insoluble gel-like structure. When used in a dry cell to back an electrolyte-soluble film it protects the soluble film, placed' adjacent to the zinc electrode, vfrom dispersion in dry cell electrolyte. vCells containing a composite diaphragm consisting of a soluble methylgcellulose f llm backed by an insolubilizedV methyl cellulose film have excellent service characteristics even after many months storage.

,In Fig. 4 is shown a round dry cell provided with a composite diaphragm of the-type shown in Fig. l embodying the invention. Adjacent to a zinc container electrode IIJA is placed a` lfilm I I of 'electrolyte-,soluble alkyl cellulose ether such as methyl cellulose. The electrolyte-soluble film II is backed by an electrolyte-insoluble film I2.A

Depolarizer mix I3, wet with electrolyte, is provided within the container electrode I adjacent to the backing film I2, and a carbon electrode I4 is positioned in the depolarizer mix I3. The cell is sealed at the top in conventional manner with 'Ia fibrous Washer I5 and a layer IB of seallng compound such as pitch or other conventional'sealing material. v

An alternative form of diaphragm embodying the invention consists of a normally electrolytesoluble film of alkyl cellulose ether such as methyl cellulose protected from excessive solution and dispersion inv dry .cell electrolyte by insolubilization of one of its surfaces. Such a film may be produced by treating one surface of an' ordinary methyl cellulose film with an insolubilizing agent suitably selected from the group of organic polybasic acids above listed. For example one surface of a dry methyl cellulose film may be subjected to the action of a 5% aqueous tannic acid solution at a temperature of about 50 C. to 60" C. poured, sprayed, or wiped on the surface to be treated and allowed to remain for a short period of time, say about 11/2 minutes before it is removed. Or the surface to be treated may be dipped into a tannic acid solution. Such treatmentproduces a tanned insoluble layer on the order of about 0.00005 inch thick on the film. A film of this type is illustrated in Fig. 2 of the drawing one side 3I of the film being untreated and the other side 32 being treated with an insolubilizing agent. When used as a dry cell diaphragm it is placed in the cell with the insolubilized surfacev adjacent to the depolarizer mix.

For some types of dry cell a single film diaphragm composed of a lm prepared from a solution containing an insolubilizing agent is entirely satisfactory. Such a diaphragm may consist ofa lm prepared from a methyl cellulose solution containing tannic acid or citric acid, for example, as above described.

This type of film is shown in Fig. 3, and Fig. 5 illustrates a battery of dry cells of the flat electrode type provided with single film diaphragms. A plurality of dry cells each comprising a flat zinc electrode 20, a flat carbon electrode 2|, a flat cake of electrolyte-wet depolarizer mix 22, and a diaphragm 23 composed of a nlm of insolubilized methyl cellulose separating the mix cake 22 from A the zinc electrode is assembled and maintained under heavy endwise pressure with the zinc electrode of one' cell adjacent to the carbon electrode of another. The assembly of cells is sealed with a deposit 24 of pitch or other sealing compound, and is placed in a suitable container 25. Films for use in the diaphragm of the invention generally should be as thin as possible consistentl results have been obtained with films about 0.003

to 0.004 inch thick. whenvdry.

The diaphragm of the invention, in any of its y various forms, completely eliminates the necessity for any cereal paste in a dry cell. Since it is prepared as a dry lm, it is easily handled, and

this feature in conjunction with the elimination of` paste makes possible much simpler assembly of cells of all shapes and sizes. l

:In particular, the diaphragm of the invention ,makes possible an improved method of manufacturing the conventional round dry cells in which the zinc electrode serves as the cell container. To assemble a cell of this type utilizing a filmtype diaphragm, an insulating bottom is placed in the container, a. film is formed into a cylinder and slipped into the container. The depolarizer mix, moistened with electrolyte, is then placed in the container, and the carbon electrode rammed into the mix. Additional electrolyte, if necessary, may then be placed on the depolarizer mix. The cell is completed and sealed in conventional manner` In each case the diaphragm film is arranged as above set forth with respect to the zinc electrode and depolarizer mix.

Dry cells provided with diaphragms Aembodying the invention but otherwise the same as conventional general purpose cereal paste type cells are far superior to the conventional cells. For example, their longer service life at different discharge rates is indicatedin the following table.

. In this table the "thin diaphragm cells referred Service in minutes of dry cells discharged through resistances indicated Resistance Cut-off Service f 0h m8 Vol! .Minutes Thin diaphragm cell 4. 0 0.90 900 D0 -L 2. l 0.67 487 Paste type cell 4.0 (l. R75 D0 l 2. l 0. 67 375 Dry cells having film-type diaphragms also have excellent keeping quality, and particularly in combination with depolarizers capable of reacting with cereal paste, have proved to' be superior in this respect and in service life to otherwise similar cells of standard paste lined construction. For example industrial flashlight cells containing active depolarizer mix and provided with double film diaphragms consistently maintain a voltage of 1.5 volts or higher for -at least 15 months, whereas the voltage of othera,ss4,sse

. 7 wise similar but paste-lined cells Vfalls below 1.5

volts after storage for as short a time as 3 to 6 months.

In Table II below are setA forth typical service life data obtained on tests of dry cells containing a composite film diaphragm having a methyl cellulose illm adjacent to the zinc containerelectrode and a citric acid insolubilized methyl cellulose film adjacent to the depolarizer mix as compared with similar tests made on cells of standard paste-lined construction. In these tests each cell after storage for the time indicated was discharged through a four ohm resistance for four minutes every fifteen minutes for eight con` seeutive hours a day. The service in minutes of each cell under these conditions is indicated in the table'for cut-oir voltages of 0.9 volt and 0.8

volt.

TABLE II v Service in minutes of dry cells before and after storage No 3 Months 6 Months Type of ce Storage Storage Storage 0.9 VOLT CUT-OFF Minn-m Minlutaes D hm mm iap gm 1,188 134 331 o 1, 244 1, 14o 474 1,581 1 444 gaiilslehm 1,344 36e Do 1,396 1, 24o- The data in Tables I and II indicate higher service output and much better service'maintenance for cells using the thin diaphragms described herein than for the conventional paste type cells. Maintenance of a working voltage above 0.9 volt is particularly important in cells and viscous. eiiectively wetting the zinc surface and providing the excellent contact between the zinc anode and the diaphragm so necessary for cell operation. The insoluble methyl cellulose backing film when wet with electrolyte slowly becomes swollen, thus immobillzing a portion of cell electrolyte. Even when saturated it has adequate wet strength and elasticity, is electrolytepermeable, permits ready din'usion of dry cell reaction products and is itself largely insoluble in cell electrolyte. Both illms are strong and ilexible when dry.

It will be apparent to those skilled in the art that other film-forming materials than methyl cellulose will have the required properties when used in a dry cell as outlined above and that although the invention has been described with particular reference to methyl cellulose. it is not limited to this material. Hydroxyethyl cellulose. salts of the cellulose ethers of glycollic acid. such as sodium carboxymethyl cellulose. vinyl polymers such as polyvinyl alcohol, polyvinyl partial acetals and partially hydrolyzed polyvinyl acetate may also be used. In double-film diaphragms it is not necessary that both films be of the same composition. Excellent results have been obtained for example, using a methyl cellulose lm adjacent to the zinc electrode and a backing iilm of hydroxyethyl cellulose insolubilized with citric acid adjacent to the depolarizer mix. Insolubillzing agents include. besides the acids enumerated above, aldehydes such as glyoxal and formaldehyde; aldehyde resins. for example, phenol-formaldehyde and initial condensation products of an amide such as urea or melamine with formaldehyde; and isocyanates. Certain films. for example oi' sodium carboxymethyl cellulose and of polyvinyl alcohol, may be insolubilized by heat alone.

for use in flashlights because of the resulting greatly increased light output, the light output of a flashlight varying as the 3.5 and 3.7th power of the voltage applied.

It has been observed that when only an electrolyte-soluble methyl cellulose diaphragm is used in a dry cell, the diaphragm slowly dissolves and is absorbed by the depolarizer mix. Absorption of diaphragm material by the depolarizer mix causes swelling of the latter even to the extent of occasional contact with the zinc surface and production of an internal short circuit. Even in the absence of such short circuit, the movement of electrolyte dispersion of methyl cellulose away from the zinc surface decreases active zinc area, promotes corrosion, increases internal resistance, and decreases cell output. The positioning of an electrolyte-insoluble backing between the electrolyte-soluble methyl cellulose and the depolarizer mix lengthens the time during which satisfactory contact with the zinc electrode is maintained, presumably because of the reduced rate of transfer of methyl cellulose into the depolarizing mix. A similar result is obtained with the insolubilized single film type diaphragm, prepared as described from alkyl cellulose ether and organic polybasic acid.

In the preferred composite diaphragm composed of an electrolyte-soluble film of methyl cellulose and an insolubilized backing lm of methyl cellulose the electrolyte-soluble methyl cellulose lm placed next the zinc surface, when exposed to electrolyte, becomes sticky adhesive Generally in the manufacture of dry cells it is the practice to amalgamate the zinc electrode for the purpose of preventing as far as possible severe localized corrosive attack of the zinc. Although this may -be done before assembly of the cell, it is most conveniently accomplished by adding a mercury salt, usually mercurio chloride, to the cell, for example in the electrolyte or. where a paste diaphragm is used, in the paste. If desired, mercuric chloride may be incorporated in the diaphragm of the invention by dissolving a quantity of it in the solution from which a film is to be cast. Usually, about two grams of mercurio chloride per liter of water is sufficient. If a composite diaphragm is to be used, it is preferable to incorporate the'mercuric chloride in the film to be placed next the zinc. Since mercuric chloride is not compatible with certain insolubilizing agents, for example, citric acid, with single-film diaphragms insolubilized with such materials,

' amalgamation is desired.

Although a composite diaphragm is shown in a round cell in Fig. 4 and a single film diaphragm is shown in flat cells in Fig. 5, it is possible and within the invention to use a composite diaphragm in flat cells and a single film diaphragm in round cells. In the drawing the thickness oi' the diaphragm is considerably exaggerated for illustration.

I claim:

l. A primary galvanic cell comprising a soluble electrode; an insoluble electrode; a depolarizer mix; an electrolyte; and a diaphragm adjacent toan'd in contact with said soluble electrode and said depolarizer mix, said diaphragm being composed of a bibulous chemically inert, nonfibrous, synthetic organic film material at least the surface portion of said diaphragm in contact with said depolarizer mix being swellable in said electrolyte but insolubilized.

2. A primary galvanic Cell as claimed in claim 1 in which said diaphragm comprises a bibulousl single film.

3. A primary galvanic cell comprising a soluble electrode; an insoluble electrode; a depolarizer mix; an electrolyte; and, separating said soluble electrode from said depolarizer mix and in contact with said soluble electrode and with said depolarizer mix, a bibulous diaphragm of alkyl cellulose ether, at least the surface of said diaphragm which is in contact with said depolarizer mix being insolubilized.

4. A primary galvanic cell comprising a zinc electrode; a carbon electrode; a depolarizer mix; an electrolyte; and a diaphragm separating said zinc electrode from said depolarizer mix; said diaphragm comprising an electrolyte-soluble lm of alkyl cellulose ether in Contact with said zinc electrode and a nonbrous, insolubilized but bibulous backing nlm in contact with said depolarizer mix.

5. A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a solid depolarizer mix; a liquid electrolyte; and a diaphragm interposed between said zinc electrode and said depolarizer mix with one of its surfaces in contact with said zinc electrode and one of its surfaces in contact with said depolarizer mix, said diaphragm being composed of nonfibrous alkyl cellulose ether film, at least the surface of said diaphragm in contact with said depolarizer mix containing an organic polybasic acid insolubilizing agent.

6. A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a solid depolarizer mix; a liquid electrolyte; and a diaphragm` interposed between said zinc electrode and said depolarizer mix with one of its surfaces in contact with said zinc electrode and one of its surfaces in contact with said depolarizer mix, said diaphragm being composed of nonflbrous alkyl cellulose ether film, at least the surface of said diaphragm in contact with said depolarizer mix containing tannic acid.

7. A primary ga-lvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a solid depolarizer mix; a liquid electrolyte; and a diaphragm interposed between said zinc electrode and said depolarizer mix with one of its surfaces in contact with said zinc electrode and one of its 4surfaces in contact with said depolarizer mix, said diaphragm being composed of nonbrous alkyl cellulose ether lm, at least the surface of said diaphragm in contact with said depolarizer mix containing citric acid.

8. A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a solid depolarizer mix; a liquid electrolyte; and a composite diaphragm interposed between said zinc electrode and said mixfsaid diaphragm comprising an electrolyte-soluble, nonbrous film of alkyl cellulose ether in contact with said zinc electrode and a backing film composed of insolubilized alkyl cellulose ether in contact with said depolarizer mix.

9. A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode;

a solid depolarizer mix, a liquid electrolyte; and a composite diaphragm interposed between said zinc electrode and said mix, said diaphragm comprising an electrolyte-soluble nonbrous film of methyl cellulose in contact with said zinc electrode and a backing film of insolubilized alkyl cellulose ether in contact with said depolarizer mix.

l0. A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a. solid depolarizer mix; a liquid electrolyte; and a composite diaphragm interposed between said zinc electrode and said mix, said diaphragm comprising an electrolyte-soluble nonbrous film of methyl cellulose in contact with said zinc electrode and, in contact with said depolarizer mix, a film of methyl cellulose containing citric acid.

11-` A primary galvanic cell comprising a soluble zinc electrode; an insoluble carbon electrode; a solid depolarizer mix; a liquid electrolyte; and a composite diaphragm interposed between said zinc electrode and said mix, said diaphragm comprising an electrolyte-soluble nonbrous film of alkyl cellulose ether in contact with said zinc electrode and a film of insolubilized hydroxy ethyl cellulose in contact with said depolarizer mix.

12. A primary galvanic cell diaphragm composed of bibulous, chemically inert, nonflbrous, synthetic organic lm material at least one surface of said diaphragm being insolubilized.

13. A primary galvanic cell diaphragm comprising a bibulous, chemically inert, nonbrous film of synthetic organic material soluble in dry cell electrolyte and a nonflbrous backing film 1nsoluble in dry cell electrolyte.

14. A primary galvanic cell diaphragm composed of bibulous, chemically inert, nonfbrous alkyl cellulose ether film, at least one surface of said diaphragm being insolubilized.

15 A primary galvaniccell diaphragm comprising a lm of electrolyte-soluble methyl cellulose and a backing layer of insolubilized methyl cellulose. g

NELSON C. CAI-ICON.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date Re. 22,065 Young Apr. 7, 1942 778,653 Gabrielson Dec. 27, 1904 1,574,844 Oppenheim Mar. 2, 1926 1,640,488 Deibel et al. Aug. 30, 1927 1,918,717 Ruben July 18, 1933 1,981,352 Fruth Nov. 20, 1934 2,034,817 Johnson Mar. 24, 1936 2,231,319 Burgess Feb. 11, 1941 2,270,200 Upright Jan. 13, 1942 2,275,281 Berl Mar. 3, 1942 2,297,248 Rudolph Sept. 29, 1942 FOREIGN PATENTS Number Country Date 394,171 Great Britain June 22, 1933 479,462 Great Britain Feb. 7, 1938 OTHER REFERENCES Young et al.: Ind. 8: Eng. Chem., vol. 29 (1937) pages 1278-9. y

Certificate of Correction Patent No. 2,534,336 December 19, 1950 NELSON C. CAHOON It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

cColumn ,7, line 45, for the word and read to; column 10, line 30, strike out material and that the said Letters Patent should he read as corrected above, so that the same may conform to the record or" the case in the Patent Oice.

Signed and sealed this 20th day of March, A. D. 1951.

THOMAS F. MURPHY,

Assistant ommz'ssz'oner of Patents. 

1. A PRIMARY GALVANIC CELL COMPRISING A SOLUBLE ELECTRODE; AN INSOLUBLE ELECTRODE; A DEPOLARIZER MIX; AND ELECTROLYTE; AND A DIAPHRAGM ADJACENT TO AND IN CONTACT WITH SAID SOLUBLE ELECTRODE AND SAID DEPOLARIZER MIX, SAID DIAPHRAGM BEING COMPOSED OF A BIBULOUS CHEMICALLY INERT, NONFIBROUS, SYNTHETIC ORGANIC FILM MATERIAL AT LEAST THE SURFACE PORTION OF SAID DIAPHRAGM IN CONTACT WITH SAID DEPOLARIZER MIX BEING SWELLABLE IN SAID ELECTROLYTE BUT INSOLUBILIZED. 